It has been discovered that the medical outcome for a patient suffering from severe brain trauma or from ischemia caused by stroke or heart attack is degraded if the patient's body temperature rises above normal (38.degree. C.). It is further believed that the medical outcome for many such patients might be significantly improved if the patients were to be cooled relatively quickly to around 32.degree. C. for a short period, e.g., 24-72 hours.
The affected organ, in any case, is the brain. Accordingly, systems and methods have been disclosed that propose cooling blood flowing to the brain through the carotid artery. An example of such systems and methods is disclosed in co-pending U.S. pat. app. Ser. No. 09/063,984, filed Apr. 21, 1998, owned by the present assignee and incorporated herein by reference. In the referenced application, various catheters are disclosed which can be advanced into a patient's carotid artery and through which coolant can be pumped in a closed circuit, to remove heat from the blood in the carotid artery and thereby cool the brain. The referenced devices have the advantage over other methods of cooling (e.g., wrapping patients in cold blankets) of being controllable, relatively easy to use, and of being capable of rapidly cooling and maintaining blood temperature at a desired set point.
As recognized in co-pending U.S. pat. app. Ser. No. 09/133,813, filed Aug. 13, 1998, owned by the present assignee and incorporated herein by reference, the above-mentioned advantages in treating brain trauma/ischemic patients by cooling can also be realized by cooling the patient's entire body, i.e., by inducing systemic hypothermia. The advantage of systemic hypothermia is that, as recognized by the present assignee, to induce systemic hypothermia a cooling catheter or other cooling device need not be advanced into the blood supply of the brain, but rather can be easily and quickly placed into the relatively large vena cava of the central venous system. Moreover, since many patients already are intubated with central venous catheters for other clinically approved purposes anyway, providing a central venous catheter that can also cool the blood requires no additional surgical procedures for those patients.
Regardless of where the cooling occurs, however, it is clear that heat must be removed from the coolant that flows through the catheter. As recognized herein, it is desirable that a cooling system for a cooling catheter consume minimal energy and space. Small size is desired because space is often at a premium in critical care units. Moreover, as also recognized herein, for patient comfort it is desirable that such a cooling system generate a minimum amount of noise. As still further understood by the present invention, it is desirable that the cooling system be easy to use by health care personnel, and that the portion of the cooling system that directly contacts the catheter coolant be disposable. We understand that if the portion of the cooling system that directly contacts the catheter coolant were not disposable, the portion undesirably would require sterilization by, e.g., autoclaving prior to reuse, because even though the coolant does not directly contact the patient but is instead contained within the catheter, the potential arises that through in-leakage or other means body fluid might indeed contaminate the coolant. Accordingly, it is the object of the present invention to address one or more of the above-noted considerations.